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Langmuir-Blodgett films of mixtures of fatty acids and a merocyanine dye with one long alkyl chain and one carboxylic group show a very anisotropic J-band near 605 nm. Merocyanine dye-fatty acid complexes and intermolecular hydrogen bonding may play a key role in metal-free J-aggregation.

A series of fluorescent coumarin derivatives 2a–e were systematically designed, synthesized and studied for their Cu2+ sensing performance in aqueous media. The sensitivities and selectivities of the on-to-off fluorescent Cu2+ sensing signal were in direct correlation with the relative arrangements of the heteroatoms within the coordinating moieties of these coumarins. Probes 2b and 2d exhibited Cu2+ concentration dependent and selective fluorescence quenching, with linear ranges of 0–80 μM and 0–10 μM, and limits of detection of 0.14 μM and 0.38 μM, respectively. Structural changes of 2b upon Cu2+ coordination were followed by fluorescence titration, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), mass spectrometry, and single crystal X-ray diffraction on the isolated Cu2+-coumarin complex. The results revealed a 1:1 stoichiometry between 2b and Cu2+, and that the essential structural features for Cu2+-selective coordination are the coumarin C=O and a three-bond distance between the amide NH and heterocyclic N. Probe 2b was also used to determine copper (II) levels in aqueous soil extracts, with recovery rates over 80% when compared to the standard soil analysis method: inductively coupled plasma-mass spectrometry (ICP-MS). [ABSTRACT FROM AUTHOR]

Abstract: Novel snowflake-like Pt–Pd bimetallic nanoclusters (Pt–PdBNC) were synthesized on a screen-printed gold nanofilm electrode (SPGFE) substrate by electrochemically reducing precursors with a new constant potential/multi-potential step deposition strategy. The electrocatalytic behavior of the modified electrode (SPGFE/Pt–PdBNC) towards H2O2 was investigated. The results indicate that the as-prepared Pt–PdBNC significantly enhances the electrochemical reduction of H2O2 in neutral media, exhibiting preferable electrocatalytic performance compared to Pt and Pd monometallic nanoclusters. Under optimum conditions, SPGFE/Pt–PdBNC offers linear responses for H2O2 in the concentration range from 0.005 to 6mM with an ultrahigh sensitivity of 804mAM−1 cm−2 and excellent selectivity. Furthermore, glucose oxidase was immobilized on the Pt–PdBNC structure, and the fabricated biosensor presents favorable properties for glucose sensing. [Copyright &y& Elsevier]

Abstract: The fabrication of a new amphiphilic block copolymer composed of a poly dl-lactic acid (PLA) hydrophobic backbone and pH dependent thermo-sensitive poly (N-isopropyl) methacrylamide-co-N-isopropylmaleamic acid-co-10-undecenoic acid (PNIPAAm-co-NIPMMA-co-UA) entities as hydrophilic domains as well as carrying 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) residues for electron spin resonance (ESR) labeling is reported. The lower critical solution temperature (LCST) of the copolymer was determined by optical absorbance measurements. The LCST was pH dependent and varied in a narrow practical range, 35.4°C at pH 5.0, 37.5°C at pH 6.5 and 39.4°C at pH 7.4, which was below, near and above nominal physiological temperature respectively. The assembly of the copolymer into micelles in aqueous solution at temperatures below the LCST was confirmed by FT-IR, 1H NMR and fluorescence spectroscopy. It is demonstrated that the anticancer drug, 5-fluorouracil (5-FU) can be loaded effectively within the polymeric micelles and released in response to environmental stimuli- namely, pH and temperature. [Copyright &y& Elsevier]

Here we presented a new facile strategy to fabricate ultrathin two-dimensional (2D) metal oxide nanosheets, by using polydopamine-coated graphene (rGO@PDA) as a template under simply wet-chemical conditions. Based on the strategy, graphene-like CeO 2 -TiO 2 mesoporous nanosheet (MNS-CeO 2 -TiO 2 ) was prepared and was loaded with dispersive Ag nanoparticles (AgNPs) to obtain effective electrocatalysts (denoted as Ag/MNS-CeO 2 -TiO 2 ) for electrochemical detection of superoxide anion (O 2 •- ). Characterizations demonstrated that MNS-CeO 2 -TiO 2 exhibited ultrathin thickness, larger specific surface area, and pore volume in comparison with its bulk counterpart. The above properties of MNS-CeO 2 -TiO 2 shorten electron transmission distance, promotes mass transfer, and is conducive to the dispersion of post-modified AgNPs. Therefore, the recommended Ag/MNS-CeO 2 -TiO 2 sensors (denoted as Ag/MNS-CeO 2 -TiO 2 /SPCE) exhibited satisfactory properties, including the sensitivity of 737.1 μA cm -2 mM -1 , the detection limit of 0.0879 μM (S/N = 3), and good selectivity. Meanwhile, the sensors also successfully realized in the online monitoring of O 2 •- released from HepG2 cells, meaning the prepared sensors had practical application potential towards the analysis of O 2 •- in biological samples., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Protein glycosylation is among the most important post-translational modifications in living organisms and the research in the field of protein glycosylation continues to garner attention. Currently, the efficient separation and enrichment of glycoproteins and glycopeptides is the primary challenge of glycoproteomics research. The number of glycoproteins is small in complex biological samples. Moreover, the presence of highly-abundant, non-glycosylated, and modified peptides makes the detection of low-abundance glycopeptides more difficult. Therefore, efficient glycopeptide enrichment methods are required to improve the detection of these compounds. The development of highly selective glycopeptide enrichment tools is important to efficiently capture glycoproteins or glycopeptides at the molecular level. Compared with traditional glycopeptide-enriched materials, covalent organic framework materials have the advantages of large specific surface area and rich modification sites, thereby exhibiting great application potential in the field of glycopeptide enrichment. In this study, a novel covalent organic framework material (O-T-D-COFs) was prepared and applied for selective glycopeptide enrichment. We applied the solvothermal method, using 2,5-dimethoxy benzene-1,4-2 formaldehyde and 1,3,5-Tris(4-aminophenyl) benzene, to synthesize imino-based COFs. The Schiff base generated via copolymerization condensation reaction constitutes the framework of the material. Next, the synthesized intermediate material was oxidized to improve the enrichment performance of the material. The functional, specific glycopeptide-binding groups were modified on the COF channels and the structure of the material was characterized using scanning and transmission electron microscope, as well as infrared spectrum and solid-state nuclear magnetic resonance. The enrichment conditions comprised the loading and elution steps, including the optimization of the elution conditions. We could observe the clear profile of 32 glycopeptides derived from human serum immunoglobulin G (IgG) tryptic digests with a significantly improved signal-to-noise ( S/N ) ratio. We applied a complex sample system to verify the enrichment selectivity of the material when the molar ratios of the IgG and bovine serum albumin (BSA) tryptic digest mixtures reached 1∶50. In addition, we investigated the enrichment performance of the detection limit, enrichment capacity, recovery rate of the material, and the application potential in glycopeptides enrichment using real samples. The material showed a good detection limit (2.5 fmol/μL), an ideal enrichment capacity (120 mg/g), and enrichment recovery (103.5%±6.6% and 101.5%±10.4%). We identified a total of 86 glycopeptides derived from 53 glycoproteins with 94 N -glycosylation sites from only 1 μL human serum. The O-T-D-COFs exhibited a good glycopeptide separation and enrichment potential, indicating that the COF material has promising application potential in glycoproteomics.

A series of fluorescent coumarin derivatives 2a - e were systematically designed, synthesized and studied for their Cu 2+ sensing performance in aqueous media. The sensitivities and selectivities of the on-to-off fluorescent Cu 2+ sensing signal were in direct correlation with the relative arrangements of the heteroatoms within the coordinating moieties of these coumarins. Probes 2b and 2d exhibited Cu 2+ concentration dependent and selective fluorescence quenching, with linear ranges of 0-80 μM and 0-10 μM, and limits of detection of 0.14 μM and 0.38 μM, respectively. Structural changes of 2b upon Cu 2+ coordination were followed by fluorescence titration, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), mass spectrometry, and single crystal X-ray diffraction on the isolated Cu 2+ -coumarin complex. The results revealed a 1:1 stoichiometry between 2b and Cu 2+ , and that the essential structural features for Cu 2+ -selective coordination are the coumarin C=O and a three-bond distance between the amide NH and heterocyclic N. Probe 2b was also used to determine copper (II) levels in aqueous soil extracts, with recovery rates over 80% when compared to the standard soil analysis method: inductively coupled plasma-mass spectrometry (ICP-MS)., Competing Interests: The authors declare no conflict of interest.

Aim: To determine whether the use of a mixed polymeric micelle delivery system based on vitamin E succinate (VES)-grafted-chitosan oligosaccharide (CSO)/VES-grafted-chitosan (CS) mixed micelles (VES-g-CSO/VES-g-CS MM) enhances the delivery of C-DMSA, a theranostic fluorescent probe, for Hg 2+ detection and detoxification in vitro and in vivo., Methods: Mixed micelles self-assembled from two polymers, VES-g-CSO and VES-g-CS, were used to load C-DMSA and afforded C-DMSA@VES-g-CSO/VES-g-CS MM for cell and in vivo applications. Fluorescence microscopy was used to assess C-DMSA cellular uptake and Hg 2+ detection in L929 cells. C-DMSA@VES-g-CSO/VES-g-CS MM was then administered intravenously. Hg 2+ detection was assessed by fluorescence microscopy in terms of bio-distribution while detoxification efficacy in Hg 2+ -poisoned rat models was evaluated in terms of mercury contents in blood and in liver., Results: The C-DMSA loaded mixed micelles, C-DMSA@VES-g-CSO/VES-g-CS MM, significantly enhanced cellular uptake and detoxification efficacy of C-DMSA in Hg 2+ pretreated human L929 cells. Evidence from the reduction of liver coefficient, mercury contents in liver and blood, alanine transaminase and aspartate transaminase activities in Hg 2+ poisoned SD rats treated with the mixed micelles strongly supported that the micelles were effective for Hg 2+ detoxification in vivo. Furthermore, ex vivo fluorescence imaging experiments also supported enhanced Hg 2+ detection in rat liver., Conclusion: The mixed polymeric micelle delivery system could significantly enhance cell uptake and efficacy of a theranostic probe for Hg 2+ detection and detoxification treatment in vitro and in vivo. Moreover, this nanoparticle drug delivery system could achieve targeted detection and detoxification in liver., Competing Interests: The authors report no conflicts of interest in this work., (© 2019 Wei et al.)